From: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Date: Wed, 31 Aug 2022 21:07:15 +0000 (-0600)
Subject: api.c: use /proc/self/mounts
X-Git-Tag: v2.0.3~16
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1686eb6f24b3f9f37e1393bd5139206dfd5e5259;p=thirdparty%2Flibcgroup.git

api.c: use /proc/self/mounts

Use /proc/self/mount instead of /proc/mounts, which is a symbolic link
to the former. The symbolic link creation can be traced back to Linux
Kernel commit 59c7572e82d6 ("proc: remove fs/proc/proc_misc.c"). Also,
the /proc/mounts are not available in the cases where the /proc is
mounted with subset=pid option.

As per kernel docs filesystems/procs.rst:
"subset=pid hides all top level files and directories in the procfs that
are not related to tasks."

Signed-off-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>
(cherry picked from commit 16be308b037bbe11a54b692c227e160f1132eabe)
---

diff --git a/src/api.c b/src/api.c
index f7b6873a..0874ca1d 100644
--- a/src/api.c
+++ b/src/api.c
@@ -1385,9 +1385,9 @@ int cgroup_init(void)
 	}
 	controllers[i] = NULL;
 
-	proc_mount = fopen("/proc/mounts", "re");
+	proc_mount = fopen("/proc/self/mounts", "re");
 	if (proc_mount == NULL) {
-		cgroup_err("Error: cannot open /proc/mounts: %s\n",
+		cgroup_err("Error: cannot open /proc/self/mounts: %s\n",
 				strerror(errno));
 		last_errno = errno;
 		ret = ECGOTHER;
@@ -1463,7 +1463,7 @@ static int cg_test_mounted_fs(void)
 	char mntent_buff[4 * FILENAME_MAX];
 	int ret = 1;
 
-	proc_mount = fopen("/proc/mounts", "re");
+	proc_mount = fopen("/proc/self/mounts", "re");
 	if (proc_mount == NULL)
 		return 0;